It will work dot to dot ( 12 o'clock crank - 6 o'clock cam) or (12 o'clock crank - 12 o'clock cam ), because cam speed is 1/2 crank speed.Will H said:
SBC Cam Sprockets Question
Setup: Number one piston at TDC, dot on crank sprocket at 12 o'clock, pin on cam at 3 o'clock, hole in cam sprocket for pin at 3 o'clock, dot on cam sprocket at 12 o'clock. this didn't seem right but both valves on number one were closed so I went right on. Aligned the dots with a straight edge and bolted it up. Motor runs fine. this is a 1970 350 block and crank. This dot setup doesn't seem right but it works. What should I know that I don't know?
Thanks, Will
Thanks, Will
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There must be a difference in the cam pin location though. The way I installed it #1 is at TDC on compression and 6 is at TDC on exhaust. If I line it up dot to dot #6 is up on compression and it would never work, I This is an Elgin czm that the machine shop supplied as a '70 LT1 replacement. I think that it's just an oddball. The specs are about 10 degrees taller than the LT1. I'm thinking about going to the Chevy store and buying an original. Thanks
You did it right SBC time on #6 when timing the cam. Just turn the engine 1 full turn then install the dizzy. The way you did it you timed it on #1
Thanks, guys. Now I can sleep o'nights. Merry Christmas.
I think the factory must have intended both dots to be at 12:00 and aligned with a straight edge of some sort, but people found it easier to do them at 6 and 12 than to have to go find a relatively straight stick. (DON'T YOU GET GREASE ON MY YARDSTICK DANG YOUR HIDE!, etc.)
Then, to complicate things, most of us learned that 6/12 was the "correct" way, and then scratched our little pointed heads half-bald wondering why the stinkin' things were always 180* out of time. Don't say YOU never did it.
Then, to complicate things, most of us learned that 6/12 was the "correct" way, and then scratched our little pointed heads half-bald wondering why the stinkin' things were always 180* out of time. Don't say YOU never did it.
Will H said:Setup: Number one piston at TDC, dot on crank sprocket at 12 o'clock, pin on cam at 3 o'clock, hole in cam sprocket for pin at 3 o'clock, dot on cam sprocket at 12 o'clock. this didn't seem right but both valves on number one were closed so I went right on. Aligned the dots with a straight edge and bolted it up. Motor runs fine. this is a 1970 350 block and crank. This dot setup doesn't seem right but it works. What should I know that I don't know?
Thanks, Will
What? There is NO WAY that the cam dot at straight up at 12 has the #1 valves closed. :nono: That is the middle of the overlap for #1 cylinder. (unless the cam gear is marked 180* wrong)
In other words, the valves on #1 cylinder are on compression/firing stroke when the piston is up and the cam dot is DOWN.
You better have them dot to dot when you time the distributor or the cam lobes and firing order will be fubar... :spank: (unless the cam gear is marked 180* wrong)
.. duh.....
Duh? When you slip in the cam with the nose pin at 3 o'[clock, and the lifters for #1 are on the cam base circle, and #1 piston is at TDC with the crank sprocket dot at 12 o'clock, and then you slip on the cam sprocket and the dot is at 12 o'clock, there is only one answer. #1 is at the end of the compression stroke and ready to fire. I used a machinist's straight edge to align the dots and completed the installation. All the literature that I had said dot to dot and in this case it was dead wrong. This was a Cloyes True Roller chain and sprocket and I doubt that it was marked wrong. That's why I posted the original question. It was a puzzlement that I had never had before.
No...Will H said:Duh? When you slip in the cam with the nose pin at 3 o'[clock, and the lifters for #1 are on the cam base circle, and #1 piston is at TDC with the crank sprocket dot at 12 o'clock, and then you slip on the cam sprocket and the dot is at 12 o'clock, there is only one answer. #1 is at the end of the compression stroke and ready to fire. I used a machinist's straight edge to align the dots and completed the installation. All the literature that I had said dot to dot and in this case it was dead wrong. This was a Cloyes True Roller chain and sprocket and I doubt that it was marked wrong. That's why I posted the original question. It was a puzzlement that I had never had before.
When the cam dowel pin is at 3 o'clock, #6 is ready to fire, not #1. You have to rotate the crank one full turn to get #1 in position to fire. This is why so many first time assemblers get the distributor 180 degrees out... they ASSUME that #1 is on the compression stroke by following the cam installation destructions... the crank sprocket mark at 12 o'clock, the cam dowel at 3 o'clock, cam sprocket mark at 6 o'clock, and install the distributor without turning crank (although you can if you point the rotor to #6 instead of #1).
Now let me ASSUME... you must have turned the crank while watching #1 INT valve open and then close (which would put the cam sprocket mark at 12 o'clock) before you stabbed the distributor... it also moves the cam dowel pin to 9 o'clock (180 degrees of camshaft revolution equals 360 degrees of crankshaft revolution). Or if you accomplished this as you described, the cam dowel pin should have been at 9 o'clock, and with the rotor pointed to #1 on the cap, you came out OK
Will H said:Duh? When you slip in the cam with the nose pin at 3 o'[clock, and the lifters for #1 are on the cam base circle, and #1 piston is at TDC with the crank sprocket dot at 12 o'clock, and then you slip on the cam sprocket and the dot is at 12 o'clock, there is only one answer. #1 is at the end of the compression stroke and ready to fire. I used a machinist's straight edge to align the dots and completed the installation. All the literature that I had said dot to dot and in this case it was dead wrong. This was a Cloyes True Roller chain and sprocket and I doubt that it was marked wrong. That's why I posted the original question. It was a puzzlement that I had never had before.
Not unless the cam gear is dotted wrong.
The cam gear only goes on one way. If the dot is in the correct place #1 cylinder is on overlap when the dot is UP. period.
Installed too many to count in the last 40 years. It is the same on all American V-8s.
Thx 71c10
Always room for manufacturing errors, and if that is the case, a MAJOR one.xntrik said:Not unless the cam gear is dotted wrong.
The cam gear only goes on one way. If the dot is in the correct place #1 cylinder is on overlap when the dot is UP. period.
Installed too many to count in the last 40 years. It is the same on all American V-8s.
Thx 71c10
Let's do this the easy way without the heads installed. You use your dial indicator to find top dead center on #1. The dot on the crank sproket will be at 12 o'clock, Then you install the cam with the pin at 3 o'clock. Then you put lifters in for 1 and 6. If the lifters for 1 are down and 6 are not down, then 1 is ready to fire, period. If the lifters on 6 are down and on 1 are not then 6 is ready to fire. In my case, when I installed the cam sproket the dot was at 12 o'clock with 1 at TDC and the lifters down. Several respondents say that Generous Motors made it this way and others have been reading too many teenage racer magazines. If you line the sprockets up dot to dot #6 will be ready to fire. I think that the guys who said that the general made it this way are right and they have eased my troubled mind. Thanks to everyone.
Heads or no heads, with the cam sprocket dot at 12 o'clock the cam dowel will be at 9 o'clock, not 3 o'clock as you describe... Have a look at this picture: http://www.edelbrock.com/automotive/timingchains.htmlWill H said:Let's do this the easy way without the heads installed. You use your dial indicator to find top dead center on #1. The dot on the crank sproket will be at 12 o'clock, Then you install the cam with the pin at 3 o'clock. Then you put lifters in for 1 and 6. If the lifters for 1 are down and 6 are not down, then 1 is ready to fire, period. If the lifters on 6 are down and on 1 are not then 6 is ready to fire. In my case, when I installed the cam sproket the dot was at 12 o'clock with 1 at TDC and the lifters down. Several respondents say that Generous Motors made it this way and others have been reading too many teenage racer magazines. If you line the sprockets up dot to dot #6 will be ready to fire. I think that the guys who said that the general made it this way are right and they have eased my troubled mind. Thanks to everyone.
Fall in and listen up. I thought that this would be clear by now. If you set it dot for dot the pin hole will be at 9 o'clock and #6 is at TDC on compression. rotate the crank one turn and the dots will be a 12 and 12 the pin hole will be at 3 o'clock and #1 is at TDC on compression. Drop in the distributor and you are good to go. Just like the earlier posters said, if you set it dot to dot you must rotate the crank one turn to time it on #1. In that case the dots will both be a 12 and the cam dowel pin will be at 3.
Deleted my duplicate post
Might as well duplicate it. It was good enough to repeat......Will H said:Deleted my duplicate post
:thumbup:
tom
71C10 said:Heads or no heads, with the cam sprocket dot at 12 o'clock the cam dowel will be at 9 o'clock, not 3 o'clock as you describe... Have a look at this picture: http://www.edelbrock.com/automotive/timingchains.html
Excuse me Drill sergeant, LOOK at the picture in the link I provided and re-read your last post. The picture of the timing set CLEARLY shows the cam dowel hole and timing marks. Explain to us why the picture does not agree with what you say?Will H said:Fall in and listen up. I thought that this would be clear by now. If you set it dot for dot the pin hole will be at 9 o'clock and #6 is at TDC on compression. rotate the crank one turn and the dots will be a 12 and 12 the pin hole will be at 3 o'clock and #1 is at TDC on compression. Drop in the distributor and you are good to go. Just like the earlier posters said, if you set it dot to dot you must rotate the crank one turn to time it on #1. In that case the dots will both be a 12 and the cam dowel pin will be at 3.
Tom, its obvious that you read the erroneous info in his post too quickly to grasp that he is wrong... and now your wrong as well. :spank:
You guy's really wanna base this on a picture in a ADVERTISMENT?
What if the picture is wrong? Oooh...My....would that ever really happen?
How about reading the instructions when you buy the part's? Then degreeing the cam to ensure the accurancy of machining.
What if the picture is wrong? Oooh...My....would that ever really happen?
How about reading the instructions when you buy the part's? Then degreeing the cam to ensure the accurancy of machining.
HOLY CRAP! (with apologies to Peter Boyle), you are correct and I (we) are not. Looking at a timing set in my hands right now proves it. I will not edit my previous post so everybody can see what a bonehead I can be.71C10 said:Excuse me Drill sergeant, LOOK at the picture in the link I provided and re-read your last post. The picture of the timing set CLEARLY shows the cam dowel hole and timing marks. Explain to us why the picture does not agree with what you say?
Tom, its obvious that you read the erroneous info in his post too quickly to grasp that he is wrong... and now your wrong as well. :spank:
tom
Look at the picture and tell me I'm wrong. Then READ the thread and tell us who is posting the wrong info...johnsongrass1 said:You guy's really wanna base this on a picture in a ADVERTISMENT?
What if the picture is wrong? Oooh...My....would that ever really happen?
How about reading the instructions when you buy the part's? Then degreeing the cam to ensure the accurancy of machining.
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